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Age, Growth, and Mortality of Fish

Age, Growth, and Mortality of Fish. Age and growth studies can be used to determine – maturity – age-related growth rates – survival/mortality rates, longevity – population age structure. Three Approaches to Aging

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Age, Growth, and Mortality of Fish

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  1. Age, Growth, and Mortality of Fish

  2. Age and growth studies can be used to determine • – maturity • – age-related growth rates • – survival/mortality rates, longevity • – population age structure

  3. Three Approaches to Aging • 1. fish held in "confinement" or marked and released at known age and then recaptured • • primarily “validation” of aging process • 2. length frequency • • assessment through modes in length-frequency distribution • • typically most valuable for one or two years • • does not work well in locations that lack well-defined growth seasons or are protracted spawners • 3. anatomical approach • • most common • • based on calcified structure (hard parts) • • structures used depends upon species and latitude • • all are invasive except for scales

  4. Length-frequency Distribution

  5. Aging Fish by Hard Parts scale => otolith => spine => fin rays => vertebrae => cleithrum => operculum => jawbone => many fishes many fishes catfish, common carp suckers, sturgeon goosefishes, skates (marine) pikes yellow perch, smallmouth bass paddlefish

  6. Fish Scale Types

  7. Features of a Ctenoid Scale radius/radii circulus/circuli edge annulus/annuli focus buried portion exposed portion ctenii

  8. Scales may have well-defined annuli in northern U.S. because of defined seasons (at least first several years of life) • Scales from fish living at more equatorial latitudes often lack annuli because of extended growing season • False annuli can be formed when other stressors become involved, such as spawning, drought, etc.

  9. Collection of Scales • often with knife • from particular areas on the fish • take several because regenerated scales will be missing some annuli

  10. Scale are read; if older and opaque, an impression is made by pressing between plastic or acetate slides Using a microfiche reader, such as in Miller Library

  11. Annulus is actually the result of closely spaced circuli Age-2 White Crappie, collected in fall (just finishing third growing season)

  12. Aging Fish by Scales 3rd year growth 2nd year growth 1st year growth

  13. White Crappie collected in July; Age 5

  14. Regenerated Scale

  15. Otoliths • lapillus, sagittus, and astericus - "ear bones" • sagittal otolith commonly used for aging Semicircular canals of inner ear

  16. Otolith removal

  17. Used whole or sectioned by saw; sometimes polishing or burning the edge is required Age-6 White Crappie, spring Age-4 WHB, spring

  18. Opercula (singular: operculum) Age-4 Yellow Perch, spring

  19. Age-4 Smallmouth Bass, spring

  20. Cross-section of a lake sturgeon fin ray showing annuli to estimate age (8yrs old).

  21. Otolith and Scale of 5 Yr Brown Trout

  22. What can be learned from aging studies: Comparison of Black Crappie (Pomoxis nigromaculatus) growth in 3 different lakes in South Dakota

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